Synthesis of cyclopentadiene derivatives

ABSTRACT

A process for preparing cyclopentadiene derivatives comprising the steps of: a) coupling a five membered heterocycle ring with a five or six membered heterocycle ring; b) reacting the obtained compound with a carbonilating system: c) reducing the obtained compound.

This application is the U.S. national phase of International ApplicationPCT/EP02/05 094, filed May 8, 2002.

The present invention relates to a process for the preparation ofcyclopentadiene derivatives of formula

wherein

-   T¹ is oxygen, sulphur or a nitrogen radical; W represents a 3 or 4    membered rest that forms a 5 or 6 membered ring. These compounds are    fit for the preparation of metallocene complexes useful as catalysts    for the polymerization of olefins.

Examples of these cyclopentadiene derivatives are known in the art. WO98/22486 relates to a class of cyclopentadiene compounds containingheteroatoms used as ligands for metallocene complexes. WO 99/24446,describes bridged and unbridged metallocenes comprising at least aheterocyclic cyclopentadiene group of one of the following formulae:

wherein one of X or Y is a single bond, the other being O, S, NR or PR,R being hydrogen or an hydrocarbon group; R², R³ and R⁴ are hydrogen,halogen, —R, —OR, —OCOR, —SR, —NR₂ or —PR₂; a is 0-4. These metallocenesmay be used as catalyst components in the polymerization of olefins,particularly in the production of homo and copolymers of ethylene.

A drawback of this kind of metallocene compounds is that the synthesisof the corresponding ligands is not simple inasmuch as it involvesseveral steps leading to low yields.

In WO 01/47939 (PCT/EP00/13191) in the name of the same applicantseveral synthetic routes have been proposed for obtainingcyclopentadienyldithiophenes compounds. All these routes involve thecondensation of two thiophene rings according to the following equation:

wherein the thiophene rings are substituted with various functionalgroups.

The same approach has been applied in Heterocycles (2000), 52(2),761-774 wherein cyclopentadienyldithiophenes have been obtained inmoderate to good yields by using the CuCl₂ mediated cyclization oforganocopper(I), or organozinc intermediates prepared fromdilithio-derivatives with CuCN or ZnCl₂.

These synthetic routes appear to involve several and complicated stepsand often the total yield is unsatisfactory.

Therefore, it would be highly desirable to provide a simple and moreefficient route to the preparation of this class of cyclopentadienylcompounds.

The applicant has surprisingly found that by reversing the order ofcondensation (i.e. in the case of cyclopentadithiophene: firstlycoupling of the two thiophene rings in position 3 and then closing thecyclopentadiene ring in position 2) it is possible to obtain higheryields with a simpler process. Moreover this process can also beadvantageously used for obtaining a broader class of compounds.

An object of the present invention is a process for preparingcyclopentadiene derivatives having formula (I)

wherein

-   T¹ is selected from the group consisting of oxygen (O), sulphur (S)    and NR, wherein R is a linear or branched saturated or unsaturated    C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl radical, optionally containing heteroatoms    belonging to groups 13-17 of the Periodic Table of the Elements;-   R¹, R², equal to or different from each other, are hydrogen or a    linear or branched saturated or unsaturated C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀alkylaryl or C₇-C₂₀-arylalkyl    radical, optionally containing heteroatoms belonging to groups 13-17    of the Periodic Table of the Elements; or they can form a C₄-C₇ ring    optionally containing O, S, N, P or Si atoms that can bear    substituents;-   W is a moiety (a) or (b)

wherein

-   T², T³, T⁴, T⁵, equal to or different from each other, are selected    from the group consisting of nitrogen (N) and CR³ wherein R³ is    hydrogen or a linear or branched saturated or unsaturated    C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl radical, optionally containing heteroatoms    belonging to groups 13-17 of the Periodic Table of the Elements; or    two adjacent R³ groups can form a C₄-C₇ ring optionally containing    O, S, N, P or Si atoms, said ring can bear substituents; preferably    not more than two groups selected from T², T³, T⁴, T⁵ are nitrogen    at the same time;-   T⁶ has the same meaning as T¹;-   T⁷ and T⁸, equal to or different from each other, are selected from    N and CR³ wherein R³ is hydrogen or a linear or branched saturated    or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl,    C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl radical, optionally containing    heteroatoms belonging to groups 13-17 of the Periodic Table of the    Elements; optionally two adjacent group R³ can form a C₄-C₇ ring    optionally containing O, S, N, P or Si atoms, said ring can bear    substituents; with the proviso that when T⁶ is different from NR, T⁷    and T⁸ are both CR³;-   preferably when T⁶ is NR, at least one group between T⁷ and T⁸ is    CR³;-   said process compres the following steps:-   a) reacting a compound of formula (II)

-   -   with a compound of formula (III)

-   -   in the presence of a coupling system, wherein W, T¹, R¹ and R²,        have the above indicated meaning and X is selected from the        group consisting of chlorine, iodine, bromine; preferably X is        bromine;

-   b) contacting the compound of formula (IV)

-   -   obtained from step a) with a carbonylating system; in order to        obtain a compound of formula (IVa)

-   -   and

-   c) treating the product obtained in step b) with a reducing agent.

When W is a moiety of formula (a)

a preferred process for preparing the cyclopentadiene compounds offormula (Ia)

wherein T¹, T², T³, T⁴, T⁵, R¹ and R² have the above indicated meaningcomprises the following steps:

-   a) reacting a compound of formula (II)

-   -   with a compound of formula (V)

-   -   in the presence of a coupling system,    -   wherein T¹, T², T³, T⁴, T⁵, R¹ and R², have the above reported        meaning and X is select from the group consisting of chlorine,        iodine, bromine; preferably X is bromine;

-   b) contacting the compound of formula (VI) obtained from step a)

-   -   with a carbonylating system; in order to obtain a compound of        formula (VIa)

-   -   and

-   c) treating the product obtained in step b) with a reducing agent.

When W is a moiety of formula (b)

-   -   a preferred process for preparing the cyclopentadiene compounds        of formula (Ib)

-   -   wherein T¹, T⁶, T⁷, T⁸, R¹ and R² have the above described        meaning comprises the following steps:

-   a) reacting a compound of formula (II)

-   -   with a compound of formula (VII)

-   -   in the presence of a coupling system, wherein T¹, T⁶, T⁷, T⁸, R¹        and R², have the above described meaning, and X is selected from        the group consisting of chlorine, iodine, bromine; preferably X        is bromine;

-   b) contacting the compound of formula (VIII) obtained from step a)

-   -   with a carbonylating system; in order to obtain a compound of        formula (VIIIa)

-   -   and;

-   c) treating the product obtained in step b) with a reducing agent.

For the purpose of the present invention the coupling system is areagent or a series of reagents that in one or more steps can couple thetwo compounds of steps a) in order to form the compound of formula (IV).Examples of coupling systems can be found in “Comprehensive OrganicTransformations” ed. 1989 VCH Publishers pages 45-70. Below is anillustrative non limiting list of coupling systems and relevantreferences.

Coupling system Reference Zn, NiBr₂, KI Chem. Lett. 917 (1979) Zn,NiCl₂(PPh₃)₂, n-Bu₄NI J. Chem. Soc.: Chem. Commun. 1476 (1987) Zn, Mg orMn; cat NiCl₂; PPh₃ J. Org. Chem. 51 2627 (1986) TiCl₃ or TiCl₄, LiAlH₄Synthesis 607 (1976) O₂, Et₃B J. Am. Chem. Soc. 93 1508 (1971) RMgBr +R’Br → R—R’ Tetrahedron Lett. 1857 (1978)

The amount of the coupling system used depends obviously on the type.Generally it is used at least one equivalent of coupling system.

A preferred step a) comprises the following substeps:

-   i) contacting the compound of formula (II) with magnesium to form    the correspondent Grignard reagent;-   ii) contacting the Grignard reagent formed in step i) with the    compound of formula (III) in the presence of a compounds selected    from the group consisting of    [1,3-bis(diphenylphosphino)propane]dichloronickel (dpppNiCl₂),    [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium (dppfPdCl₂),    tetrakis(triphenylphosphino)palladium; preferably with dpppNiCl₂.

Alternatively step a) comprises the following substeps

-   i) contacting the compound of formula (III) with magnesium to form    the correspondent Grignard reagent;-   ii) contacting the Grignard reagent formed in step i) with the    compound of formula (II) in the presence of a compounds selected    from the group consisting of    [1,3-bis(diphenylphosphino)propane]dichloronickel (dpppNiCl₂),    [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium (dppfPdCl₂),    tetrakis(triphenylphosphino)palladium; preferably with dpppNiCl₂.

The Grignard reagents are obtained with process known in the art such asthose cited by Kagan et al. (Heterocycles, 1986, 2261) or Riecke et al.(J. Org. Chem., 1997, 6921). The preferred process uses magnesiumactivated by 10% of dibromoethane in tetrahydrofuran as described inWeygand-Hilgetag, Organisch-Chemische Experimentierkunst, 3 Auflage,1964. When W is equal to the moiety (b) and the compounds of formula(II) and (III) are the same a further preferred step a) comprisescontacting two equivalents of the compound of formula (II) with acoupling system comprising

-   i) an alkali or alkaline earth-metal, preferably zinc (zinc powder    or granules (mossy zinc));-   ii) a compound of formula QG₃ or a compound of formula G₂Q-A-QG₂    wherein Q is a phosphorus or nitrogen atom, G equal to or different    from each other are selected from the group consisting of linear or    branched saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl,    C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl, C₇-C₂₀-arylalkyl radical, optionally    containing heteroatoms belonging to groups 13-17 of the Periodic    Table of the Elements and A is a group linking the two Q atoms; it    can be a divalent organic radical selected from the group consisting    of C₁-C₂₀-alkylene, C₃-C₂₀-cycloalkylene, C₂-C₂₀-alkenylene,    C₆-C₂₀-arylene C₇-C₂₀-alkylarylene, C₇-C₂₀-arylalkylene divalent    radical, optionally containing heteroatoms belonging to groups 13-17    of the Periodic Table of the Elements; A can be also a different    group such as a complex that has the two radicals G₂Q as    substituents such as a ferrocene group to form for example    1,1′-bis(diphenylphosphino)ferrocene; preferably the compound used    has formula QG₃; wherein preferably Q is phosphorous and at least    one G is phenyl or a substituted phenyl, more preferably QG₃ is    triphenylphosphine; and-   iii) a transition metal halogenide of formula JZ_(e) wherein J is a    transition metal, preferably it is a transition metal of groups 4-11    of the periodic table, Z is chlorine, bromine, iodine and e is equal    to the oxidation state of the metal J, preferred compound of formula    JZ_(e) is NiBr₂.

Step a) is carried out at a temperature range of from −78 C. to 100° C.,preferably from 10° C. to 60° C. Usually aprotic solvents are used, suchas toluene, diethyl ether, hexane, tetrahydrofuran, dimethyl formamide,etc. The product obtained from step a) is purified by process known inthe art such as filtration, crystallization, chromatography,distillation; otherwise it is used as such.

For the purpose of the present invention the carbonylating system isdefined as reagent or a series of reagents that in one or more steps canclose the five membered ring in order to obtain compound of formula(IVa). Carbonylating step b) depends from the carbonyl system used. Apreferred step b) comprises the following substeps:

-   i) contacting the compound of formula (IV) obtained from step a)    with two equivalents of a base; and-   ii) treating the dianionic compound obtained from step i) with a    compound of formula (IX)

-   -   wherein R⁴ and R⁵ equal to or different from each other are        selected from the group consisting of hydrogen, chlorine,        bromine, iodine, OR and NR₂, wherein R is described above;        preferably R⁴ is chlorine bromine, iodine CF₃, Cl₃ or OR, more        preferably chlorine or OCH₂CH₃; preferably R⁵ is selected from        the group consisting of CF₃, Cl₃, OR and NR₂, wherein R is        described above, more preferably R⁵ is NR₂, even more preferably        R⁵ is N(CH₃)₂;

An alternative embodiment for carrying out step b) comprises thefollowing substeps:

-   i) contacting the compound of formula (IV) obtained from step a)    with two equivalents of a base and subsequently with one equivalent    of a compound selected from chlorine, bromine or iodine in order to    obtain an anionic monohalogenated derivative; and-   ii) treating the an anionic monohalogenated compound obtained from    step i) with a compound of formula (IXa)    [M_(m)L_(j)(CO)_(n)]^(a)  (IXa)    -   wherein M is a transition metal of groups 4-11 of the periodic        table; L is a ligand that coordinates the metal M that can be        neutral or with a positive or negative charge; a ranges from −4        to +4, it represents the charge of the complex when a is 0 the        complex is neutral; m ranges from 1 to 20; j ranges from 0 to        30; and n ranges from 1 to 50; preferably a ranges from −2 to        +2; m ranges from 1 to 10; j ranges from 0 to 5 and n ranges        from 1 to 20.

A further alternative embodiment for carrying out step b) comprises thefollowing substeps:

-   i) contacting the compound of formula (IV) obtained from step a)    with a halogenating compound and subsequently with one equivalent of    a base in order to obtain an anionic monohalogenated derivative; and-   ii) treating the an anionic monohalogenated compound obtained from    step i) with a compound of formula (IXa)    [M_(m)L_(j)(CO)_(n)]^(a)  (IXa)    -   wherein M is a transition metal of groups 4-11 of the periodic        table; L is a ligand that coordinates the metal M that can be        neutral or with a positive or negative charge; a ranges from −4        to +4, it represents the charge of the complex when a is 0 the        complex is neutral; m ranges from 1 to 20; j ranges from 0 to        30; and n ranges from 1 to 50; preferably a ranges from −2 to        +2; m ranges from 1 to 10; j ranges from 0 to 5 and n ranges        from 1 to 20.

The base used in step b) is preferably selected from hydroxides andhydrides of alkali- and alkaline-earth metals, metallic sodium andpotassium and organometallic lithium compounds. Most preferably, saidbases are methyllithium, n-butyllithium, or tertbutyllithium optionallyactivated with tetramethylethylene diamine (TMEDA).

Example of halogenating compounds are described in “ComprehensiveOrganic Transformations” ed. 1989 VCH Publishers pages 315-318, such asfor example chlorine, bromine, iodine CuCl₂, CBr₄, N-bromo-succinimide,N-chloro-succinimide. Non limitative example of compounds of formula(IX) are:

-   carbethoxyimidazole, triphosgene, ethyl N,N-dimethylcarbamate,    chloride of N,N-dimethylcarbamic acid.

Non limitative example of ligands L are; halogen, hydrogen, nitrogen,amines, phosphine, cyclopentadienyl derivatives, octadienes.

Non limitative example of compound of formula (IXa) are

-   C(CO)₆, Cr(CO)₆, Cr(CO)₅H₂, Mn(CO)₅H, Mn(CO)₅I, Mn₂(CO)₁₀, Mn₂(CO)₈H    ₂Fe(CO)₅,-   Fe(CO)₄H₂, Fe(CO)₂X₂, Fe(CO)₄X₂, Fe(CO)₅X₂, Fe₂(CO)₉,    Co(CO)₄H,Co(CO)₂X₂,-   Co(CO)₄X₂, Co(CO)₅X₂, Co₂(CO)₆, Ni(CO)₄, Ni₂(CO)₆H₂, Fe₃(CO)    ₁₂,[Fe(CO)₁₁H]^(−,)-   Os₃(CO)₁₂, [Re₃(CO)₁₂H₆]⁻, [Re₄(CO)₁₆]²⁻, Co₄(CO) ₁₂,    [Fe₄(CO)₁₃]^(2−, Os) ₅(CO)₁₆,-   [Os₅(CO)₁₅I]⁻, [Ni₅(CO)₁₂]²⁻, [Fe₅C(CO)₁₅]⁻, Rh₆(CO)₁₆, Rh₆(CO)₁₅I,    [Co₆(CO)₁₄]⁴⁻,-   [Fe₆C(CO)₁₆]²⁻, [Co₆H(CO)₁₅]⁻, [Rh₆C(CO)₁₅]²⁻, [Co₆N(CO)₁₅]⁻,    Os₆(CO)₁₈;-   wherein X is chlorine, bromine, iodine.

Step b) is carried out to a temperature range of from −78 C. to 100° C.preferably from −20° C. to 30° C. Usually aprotic solvents are used suchas diethyl ether, hexane, toluene, tetrahydrofuran, dimethoxyethane anddioxane. The product obtained from step b) is purified by process knownin the art such as filtration, recrystallization, chromatography,distillation; or alternatively is used as such.

In step c) various reducing agent known in the art can be used. Exampleof suitable reducing agent used in step c) are described in“Comprehensive Organic transformations” ed. 1989 VCH Publishers pages35-40. Preferred reducing agents are LiAlH₄/AlCl₃ and N₂H₄/base, such asNaOH and KOH.

The solvent for carrying out step c) depends upon the reducing agentused. For example when LiAlH₄/AlCl₃ is used the reaction is carried outis an aprotic solvent either polar or apolar such as tetrahydrofuran,dimethoxyethane, diethyl ether, toluene, pentane, hexane. When N₂H₄/baseis used a protic solvent such as water or diethylene glycol can also beused, optionally in the presence of a phase transfer agent. Thetemperature depends from the reducing agent used, it generally rangesfrom −80 C. to 300 C., preferably from 0° C. to 150 C.

Preferably the step c) comprises the following substeps:

-   i) contacting the compound of formula (VIa) with N₂H₄;-   ii) adding a solution of KOH in water; and-   iii) filtering the solid and recovering the product.

Step i) is preferably carried out in water, toluene or diethyleneglycol; step ii) is preferably carried out in the presence of a phasetransfer agent, preferably diethylene glycol.

The product obtained from step c) is purified by process known in theart such as filtration, crystallization, column chromatography,preferably by filtration.

In the compound of formula (Ia):

-   T¹ is preferably sulphur or oxygen, more preferably is sulphur; T²    is NCH₃ or CH, more preferably CH; T³, T⁴, T⁵ are preferably CH;-   R¹ and R² are preferably hydrogen methyl, ethyl, phenyl,    trimethylsilyl group or together form a benzene ring; more    preferably R¹ is methyl and R² is hydrogen or together form a    benzene ring;-   In the compound of formula (Ib) preferably:-   T¹ and T⁶ are the same and they are sulfur or oxygen, more    preferably they are sulfur;-   T⁷ and T⁸ equal to or different from each other are preferably CR³;    more preferably T⁸ is CH or form with T⁷ a benzene ring;-   T⁷ is preferably hydrogen C—CH₃, C—CH₂CH₃, C—C₆H₅, Csi(CH₃)₃ or form    with ring,-   more preferably T⁷ is C—CH₃ or form with T⁸ a benzene ring;-   R¹ and R² are preferably hydrogen methyl, ethyl, phenyl,    trimethylsilyl group or together form a benzene ring; more    preferably R¹ is methyl and R² is hydrogen or together form a    benzene ring;-   Non limitative examples of compounds of formula (I) are:

Compounds of formula (II) and (III) are commercially available or can beobtained with processes known in the art, in particular compounds offormula (II) are described in WO 98/22486, WO 99/24446 PCT/EP00/13191,and EP 938491.

Compounds of formula (I) can be used as ligands for the synthesis ofmetallocene complexes, such as those described in WO 98/22486 WO99/24446 and PCT/EP00/13191. These complexes are useful as catalystcomponents for polymerizing alpha-olefins. The syntheses of themetallocene compounds starting from the compounds of the presentinvention are described in the above mentioned applications. Generally,the compounds of formula (I) can be treated with a base and thencontacted with a compound of formula YL′Cp wherein Y is halogen,preferably chlorine, L′ is a suitable bridge and Cp is a substituted orunsubstituted cyclopentadienyl radical. The obtained bridged ligand isthen treated with two equivalents of a base and contacted with thecompound of formula ML″₄ wherein M is titanium, zirconium or hafnium andL is generally halogen, preferably chlorine. For unbridged metallocenecompounds the compound of formula (I) is treated with a base and thenthe correspondent anion is contacted with a compound of formula ML″₄.

A further object of the present invention is a compound of formula (X)

wherein R¹, R² and R³ have been described above with the proviso that atleast one R¹, R² or R³ is different from hydrogen.

A still further object of the present invention is a compound of formula(XI)

wherein R¹, R² and R³ have been described above and T⁹ is O (Oxygen) orS (sulphur).

The following examples are given for illustrative purposes and are notintended to limit the scope and spirit of the invention.

EXAMPLES

General Procedures.

All operations were performed under nitrogen by using conventionalSchlenk-line techniques. Solvents were purified by degassing with N₂ andpassing over activated (8 hours, N₂ purge, 300° C.) Al₂O₃, and storedunder nitrogen. n-BuLi (Aldrich) was used as received.

Synthesis of ethyl N,N-dimethylcarbamate

85 mL (0.89 mol) of ethyl chloroformate was added dropwise to 500 mL 33%aqueous dimethylamine at 0-10° C. within 1.5 h. Resulting mixture wasstirred in 4 hours, and then it was extracted with methylene chloride (4portions of 250 mL). The extracts were washed with water, 5% HCl, 3%KHCO₃, with water again and finally was dried by MgSO₄. The solution wasevaporated and distilled at 144° C. to give 84 g (80%) of the product.

¹H NMR (CDCl₃): 4.12 (q, 2H); 2.90 (br.s., 6H); 1.25 (t, 3H)

¹³C NMR (CDCl₃): 156.6; 60.8; 35.9 (br.s); 35.4(br.s); 14.4

Synthesis of 4-bromo-2-methylthiophene

i) Bromination of 2-thiophenecarboxaldehyde

668 g (5 mol) of AlCl₃ were suspended in 1 L of chloroform. 224 g (2mol) of 2-thiophenecarboxaldehyde (Lancaster of 98% purity) were addeddropwise within 1 hour to the cooled resulting mixture under stirring.The suspension was stirred 1 hour, then 114 mL (2.2 mol) of Br₂ wereadded dropwise in 1.5 h and the reaction was stirred overnight.

The resulting mixture was poured into the beaker with 1 kg ice and 200mL of 32% HCl under stirring. The organic phase was isolated, washedwith water, then with 5% aqueous NaHCO₃, then with 5% aqueous, then withwater again. The resulting solution was dried with MgSO₄ and evaporated.The 4-bromo-2-thiophenecarboxaldehyde crystallises spontaneously. It wasused without further purification. Yield 80-86%.

¹H NMR (CDCl₃): 9.88 (d, 1H); 7.69(d, 1H); 7.66 (t, 1H).

¹³CNMR (CDCl₃): 181.4; 143.6; 137.5; 131.9; 111.1

ii) Reduction of 4-bromo-thiophenecarboxaldehyde

191 g (1 mol) of 4-bromo-2-thiophenecarboxaldehyde, 500 mL of diethyleneglycol and 146 mL (3 mol) of hydrazine monohydrate were placed in abulb. This suspension was refluxed for 1 h and then cooled to roomtemperature. The resulting mixture was treated with a solution of 342 g(6 mol) of KOH in 400 mL of water. The mixture was carefully heated toreflux and after evolution of nitrogen is over the product was distilledwith water from the reaction-bulb. The so distilled two-phase mixturewas treated with 200 mL of CH₂Cl₂, organic phase was isolated, washedtwice with water, dried over MgSO₄, evaporated and distilled at 60-64°C./10 torr. Total yield ca. 70% for two steps starting from2-thiophenecarboxaldehyde.

¹H NMR (CDCl₃): 7.02 (d, 1H); 6.73 (q, 1H); 2.52 (d, 3H)

¹³C NMR (CDCl₃): 141.0; 127.7; 120.2; 108.9; 15.2

Synthesis of 4-bromo-2-methylthiophene (alternative route)

i) 4-bromothiophenecarboxaldehyde

A mixture of 119 g (892 mmol) of AlCl₃ was suspended into 150 mL ofdichloromethane. To this mixture was added 66.6 g (595 mmol) of2-thiophenecarboxaldehyde in a way the temperature raised to reflux.After addition the mixture was stirred for 30 minutes at roomtemperature. Then 33.8 mL (654.5 mmol) of Br₂ was added and the mixturewas stirred overnight and poured into a mixture of 250 g of ice and 50mL of concentrated HCl. The organic layer was isolated and washedsubsequently with 300 mL of 5 w % NaHCO₃ and 300 mL of 5 w % aqueousKOH. The organic layer was isolated, dried over MgSO₄ and concentratedin vacuo. The resulting solid (115 g, crude yield 100%) contained 94% of4-bromo-2-thiophenecarboxaldehyde, 5% of4,5-dibromo-2thiophenecarboxaldehyde and 1% of starting material.

ii) 4-bromo-2-methylthiophene

To 1.3 mL (26.2 mmol) of hydrazine monohydrate was added 5 g (26.2 mmol)of 4-bromo-2-thiophenecarboxald in 5 mL of toluene at 90° C. After 1 hstirring at this temperature 1.7 g (26.2 mmol) of KOH was added as asolid and 2 mL of diethylene glycol was added subsequently. Gasformation was noticed. After 2 h the reaction was complete. The toluenelayer was isolated and the glycol layer was extracted twice with 5 mL oftoluene, yielding 5.6 g of 71 w % solution of 4-bromo-2-methylthiophene.The contained yield was 86% (according to ¹H-NMR) and the purity 97%.The product contained still 2% of 4,5-dibromo-2-methylthiophene.

iii) 4-bromo-2-methylthiophene (alternative process)

A reactor equipped with stirrer, reflux condenser and thermometer wasloaded with 392 g (1.97 mol) of 4-bromo-2-thiophenecarboxaldehyde and220 g (12.2 mol) of water. This slurry was heated to 100° C. The4-bromo-2-thiophenecarboxaldehyde melted and a suspension was formedunder stirring. At this temperature 106 g (2.07 mol) of hydrazinemonohydrate was dosed to the mixture over a period of 30 min. Anexotherm was observed and the mixture was refluxing. After 1 h postreaction time at 100° C., 353 g (3.3 mol) of diethylene glycol was addedslowly. Hereafter a solution of 116 g (2.1 mol) of KOH in 135 g of waterwas dosed slowly (1 h) to the reaction mixture. After 10% of the basewas added slow evolution of gas (nitrogen) was observed from thereaction mixture. After the KOH/water addition, the mixture was kept at100° C. for 24 h while stirring. Hereafter the mixture was allowed tocool to ambient temperature and the phases were separated. The organicphase was washed twice with 100 g of water. Analyses of the organiclayer showed complete conversion and a product purity of the formed4-bromo-2-methylthiophene of 98%. The yield was 98%.

Example 1 Synthesis of 2-methyl-8H-indeno[2,1-b]thiophene

Step a) 2-methyl-4-phenylthiophene

A solution of PhMgBr (prepared from 1.65 g of Mg (0.0678 mol) and 10.64g of PhBr (0.0678 mol) in 40 mL of diethyl ether) was added to a mixtureof 10 g (0.0565 mol) of 4-bromo-2-methylthiophene and 0.62 g (0.0012mol) of NiCl₂dppp in 50 mL of ether under stirring at reflux. Thereaction mixture was refluxed for additional 3 h and then stirredovernight. The resulting mixture was treated with 10% aqueous NH₄Cl, theorganic layer was separated, washed with 10% aqueous NH₄Cl and thendried with anhydrous Na₂SO₄. Solvent was evaporated, the residue wasrecrystallized from methanol. Yield 6.8 g (70%) of colorless crystals.

¹H NMR (CDCl₃, 30° C.) d: 7.65 (d, 2H), 7.47 (d, 2H), 7.37 (t, 1H), 7.28(m, (s, 1H).

Step b) 2-methyl-8H-indeno[2,1-b]thiophen-8-one

A solution of 12.88 g (0.074 mol) of 2-methyl-4-phenylthiophene, 23.4 mL(0.16 mol) of TMEDA in 200 mL of diethyl ether (ether) was treated with100 mL (0.16 mol) of 1.6M BuLi in hexane under stirring at −40° C. Thenthe reaction mixture was allowed to warm up to room temperature (r.t.)and was stirred for 3 h (white precipitate forms). The reaction mixturewas cooled to −40° C. and treated with 8.76 g (0.075 mol) of ethylN,N-dimethylcarbamate in 25 mL of ether. Then the reaction mixture wasallowed to warm up to r.t. and was stirred overnight. Resulting mixturewas treated with 10% aqueous NH₄Cl, the organic layer was separated andthe organic phase was washed with 10% aqueous solution of NH₄Cl and thendried by anhydrous Na₂SO₄. Solvent was evaporated and the residue waswashed with methanol. Yield 6.8 g (46%) of red crystals.

¹H NMR (CDCl₃, 30° C.) d: 7.44 (d, 1H), 7.29 (t, 1H), 7.14 (t, 1H), 7.07(d, 2.55 (s, 3H).

step c) 2-methyl-8H-indeno[2,1-b]thiophene

A mixture of 6.83 g (0.034 mol) of2-methyl-8H-indeno[2,1-b]thiophen-8-one and 9.1 mL (0.182 mol) ofhydrazine monohydrate in 91 mL of diethylene glycol was stirred at 80°C. for 40 min and then refluxed for 1 h. The resulting mixture wascooled to room temperature, treated with a solution of 9.5 g (0.169 mol)of KOH in 34 mL water and then refluxed for 2 h.

The resulting mixture was poured into 600 mL of water, the precipitatewas filtered, washed 5 times with 200 mL of water and dried. Yield 5.8 g(92%).

¹H NMR (CDCl₃, 30° C.) d: 7.53 (d, 1H), 7.51 (d, 1H), 7.37 (t, 1H), 7.23(t, 7.01 (m, 1H), 3.81 (s, 2H), 2.61 (s, 3H).

Example 2 Synthesis of 5,8-dimethyl-5,6-dihydroindeno[2,1-b]indole3-bromo-1-methyl-1H-indole

A solution of 1.2 mL (0.0229 mol) of Br₂ in 40 mL of pyridine was addedto a solution of 3.0 g (0.0229 mol) of N-methylindole in 30 mL ofpyridine. The reaction mixture was stirred for 1 h, then it was treatedwith 100 mL of cold ether and the suspension was filtered. Cold solutionwas washed with 100 mL of 5% aqueous NaOH, with water (50 mL) andfinally was dried over anhydrous sodium sulfate. The resulting solutionwas evaporated to give 4.31 g (89%) of product as brown oil.

¹H NMR (CDCl₃, 25° C.) δ: 7.50 (d, 1H); 7.40 (m, 2H); 7.26 (m, 1H); 7.08(s,1H); 3.77 (s, 3H).

step a) 1-methyl-3-(4-methylphenyl)-1H-indole

A mixture of 4.31 g (0.02 mol) of 3-bromo-1-methyl-1H-indole and 0.22 g(0.0004 mol) of NiCl₂dppp was added to a solution of p-TolylMgBr inether (prepared from 0.6 g of Mg (0.025 mol) and 4.21 g of TolylBr(0.024 mol) in 40 mL of ether) under stirring. The reaction mixture wasstirred overnight. The resulting mixture was treated with 10% aqueousNH₄Cl, the organic layer was separated, washed with 10% aqueous NH₄Cland then dried over anhydrous Na₂SO₄. The solution was evaporated togive an oil that crystallized. The product was washed with methanol anddried. Yield 2.2 g (49%) of colorless crystalline solid.

¹H NMR (CDCl₃, 25° C.) δ: 8.14 (d, 1H); 7.75 (d, 2H); 7.44 (m, 5H); 7.26(m, 1H); 3.90 (s, 3H); 2.58 (s, 3H).

step b) 5,8-dimethylindeno[2,1-b]indol-6(5H)-one

A solution of 2.19 g (0.00991 mol) of1-methyl-3-(4-methylphenyl)-1H-indole and 3.24 mL (0.0218 mol) of TMEDAin 30 mL of ether was treated with 13.6 mL (0.0218 mol) of 1.6M BuLi inhexane under stirring at −40° C. Then the reaction mixture was allowedto warm up to r.t. and stirred for 4 h. The reaction mixture was cooledto −60° C. and treated with 1.16 g (0.00991 mol) ethylN,N-dimethylcarbamate in 5 mL of ether. Then the reaction mixture wasallowed to warm up to r.t. and was stirred overnight. Resulting mixturewas treated with 50 mL of 10% aqueous NH₄Cl. The violet precipitate wasseparated, washed twice with water and dried. Yield 1.04 g (42%).

¹H NMR (CDCl₃, 25° C.) δ: 7.58 (d, 1H); 7.27 (t, 1H); 7.22 (d, 1H); 7.147.09 (s, 1H); 6.98 (d, 1H); 6.92 (d, 1H); 3.80 (s, 3H); 2.26 (s, 3H).

Step c) 5,8-dimethyl-5,6-dihydroindeno[2,1-b]indole

A mixture of 1.04 g (0.0042 mol) of5,8-dimethylindeno[2,1-b]indol-6(5H)-one and 1.12 mL (0.0224 mol) ofhydrazine monohydrate in 20 mL of diethylene glycol was stirred at 80°C. for 1 h and then refluxed for 1 h. The resulting mixture was cooledto r.t., treated with a solution of 1.2 g (0.0214 mol) of KOH in 5 mL ofwater and then it was refluxed for 2 h. The resulting mixture was pouredinto 100 mL of water, the precipitate was filtered, washed 5 times with50 mL of water and dried. Yield 0.84 g (86%) of greenish solid.

¹H NMR (CDCl₃, 25° C.) δ: 7.88 (m, 1H); 7.55 (d, 1H); 7.36 (m, 1H); 7.263H); 7.18 (d, 1H); 3.77 (s, 3H); 3.64 (s, 2H); 2.44 (s, 3H).

Example 3 Synthesis of2,5-dimethyl-7H-thieno[3′,2′:3,4]cyclopenta[1,2-b]thiophene

Step a) 2,2′-dimethyl-4,4′-dithienyl

A suspension of 21.4 g (0.53 mol) of Mg in 50 mL of THF was treated with4 mL (45 mmol) of 1,2-dibromoethane. The mixture starts to warm and thegas starts to bubble. After the evolution of the gas is over, theresulting mixture was treated with the solution of 253 g (1.43 mol) of4-bromo-2-methylthiophene and 9.5 mL (110 mmol) of dibromoethane in 400mL of THF. After Mg is dissolved the reaction mixture was allowed tocool to room temperature, treated with 700 mL of THF and with 3.8 g(14.3 mmol) of NiCl₂dppp and stirred overnight. The resulting mixturewas dried three times with 2 L of 10% aqueous NH₄Cl at vigorousstirring, organic phase with suspended crystalline product was isolated,washed twice with 2 L of water and treated with 600 mL of hexane. Thesuspension was filtered. The product was washed twice with hexane on thefilter and dried. Yield of first portion 92 g. The filtrate wasisolated, evaporated and recrystallyzed from 1 L of ethanol. Secondportion of compound weights 14 g. Total yield of dithienyl 106 g (77%).

¹H NMR (CDCl₃): 7.08 (d, 1H); 6.98(quintet, 1H); 2.52(d, 3H)

¹³CNMR (CDCl₃): 140.1; 137.1; 124.4; 117.1; 15.3

Step b) 2,5dimethyl-7H-thieno[3′,2′:3,4]cyclopenta[1,2-b]thiophen-7-one

A mixture of 48.6 g (250 mmol) of 2,2′-dimethyl-4,4′-dithienyl, 400 mLof ether and 83 mL (550 mmol) of TMEDA was placed into the bulb, theresulting suspension was cooled to −20° C. and then treated with 250 mL(550 mmol) of 2.2M BuLi in hexane. The mixture was allowed to warm up tor.t. and was stirred for 3 hours. The reaction mixture was treated with29.3 g (250 mmol) of carbamate (EtO)C(O)NMe₂ in 600 mL of ether and thenwas stirred in 40 hours.

The resulting mixture was poured into 2 L of saturated aqueous solutionof NH₄Cl under shaking or stirring. Organic phase containing some of theprecipitated product was isolated, washed with 1 L of water, treatedwith 100 mL of hexane and then filtered. The precipitate was washed withwater, twice with 100 mL of hexane and dried. Yield of first portion is31 g. Filtrate was evaporated up to volume of 200 mL to give asuspension. This suspension was filtered, washed with hot hexane anddried. The yield of second portion is 14 g. Total yield 45 g (82%).

¹H NMR (CDCl₃): 6.58(q, 1H); 2.50 (d, 6H);

¹³C NMR (CDCl₃): 178.8; 152.6; 152.2; 133.0; 118.6; 16.1

Step c) Reduction of2,5-dimethyl-7H-thieno[3′,2′:3,4]cyclopenta[1,2-b]thiophene

A mixture of 45 g (205 mmol) of2,5-dimethyl-7H-thieno[3′,2′:3,4]cyclopenta[1,2-b]thiophen-7-one, 600 mLof diethylene glycol and 70 mL of hydrazine monohydrate was placed intothe bulb. The mixture was warmed to 80° C. and kept at this temperaturein 1 h at stirring. Then the mixture was intensively refluxed in 1 h,cooled to r.t. treated with solution of 70 g KOH in 230 mL of water. Theresulting mixture was carefully heated and the gas started to bubble.The mixture was refluxed for 2 hours, then it was cooled to 70-80° C.and poured into 3 L water. The precipitate was decanted, filtered,washed 7 times with 200-300 mL of water and dried. Yield 32 g (78%).

¹H NMR (CDCl₃): 6.81 (q, 2H); 3.72 (s, 2H); 2.58 (d, 6H)

¹³C NMR (CDCl₃): 143.6; 142.1; 140.1; 116.4; 33.1; 15.9

The yields of the various steps of the process are compared in table 1.

Example 4 Synthesis of 6-(tert-butyl)-2-methyl-8H-indeno[2,1-b]thiophene

Step a) 4-[4-(tert-butyl)phenyl]-2-methylthiophene

To a mixture of 8.8 g (0.05 mol) of 4-bromo-2-methylthiophene and 0.27 g(0.0005 mol) of NiCl₂dppp in 40 mL of ether a solution of para-tBuPhMgBr(prepared from 1.46 g of Mg (0.06 mol) and 12.73 g of para-tBuPhBr (0.06mol) in 35 mL of ether) was added under stirring at reflux. The reactionmixture was refluxed for additional 3 h and then stirred overnight. Theresulting mixture was treated with 10% aqueous NH₄Cl, the organic layerwas separated, washed with 10% aqueous NH₄Cl and then dried overanhydrous Na₂SO₄. Solvent was evaporated, the residue was recrystallizedfrom methanol. Yield 2.27 g (20%) of colorless crystals.

¹H NMR (CDCl₃, 30° C.): 7.55 (d, 2H), 7.46 (d, 2H), 7.21 (s, 1H), 7.10(s, 1H),2.57 (s,3H), 1.40 (s, 9H).

Step b) 6-(tert-butyl)-2-methyl-8H-indeno[2,1-b]thiophen-8-one

A solution of 2.23 g (0.01 mol) of4-[4-(tert-butyl)phenyl]-2-methylthiophene, 2.97 mL (0.02 mol) of TMEDAin 30 mL of ether was treated with 13 mL (0.02 mol) of 1.6M BuLi inhexane under stirring at −40° C. Then the reaction mixture was allowedto warm up to r.t. and stirred for 3 h. The reaction mixture was cooled−40° C. and treated with 1.17 g (0.01 mol) of ethylN,N-dimethylcarbamate in 10 mL of ether. Then the reaction mixture wasallowed to warm up to r.t. and was stirred overnight. Resulting mixturewas treated with 10% aqueous NH₄Cl, organic layer was separated, washedwith 10% aqueous NH₄Cl and then dried over anhydrous Na₂SO₄. Solvent wasevaporated, the residue was washed with methanol. Yield 2.4 g (about100%) of red oil.

¹H NMR (CDCl₃, 30° C.): 7.53 (d, 1H), 7.29 (dd, 1H), 7.01 (d, 1H), 6.80(d, 1H),2.55 (d,3H), 1.33 (s, 9H).

Step c) 6(tert-butyl)-2-methyl-8H-indeno[2,1-b]thiophene

A mixture of 2.40 g (0.0095 mol) of6-(tert-butyl)-2-methyl-8H-indeno[2,1-b]thiophen-8-one and 2.6 mL (0.05mol) of hydrazine monohydrate in 25 mL of diethylene glycol was stirredat 80° C. in 40 min and then refluxed for 1 h. The resulting mixture wascooled to r.t., treated with a solution of 2.68 g (0.035 mol) of KOH in9.4 mL of water and subsequently refluxed for 2 h. The resulting mixturewas poured in 150 mL of water, the precipitate was filtered, washed 5times with 100 mL of water and dried. Yield 1.25 g (54%).

¹H NMR (CDCl₃, 30° C.): 7.56 (s, 1H), 7.45 (d, 1H), 7.35 (dd, 1H), 6.96(q, 1H),3.81 (s,2H); 2.60 (d, 3H), 1.42 (s, 9H).

Example 5 Synthesis of2,5-dimethyl-7H-cyclopenta[1,2-b;3,4-b′]dithiophene

Step a) 2,2′-dimethyl-4,4′-dithienyl

In a Schlenk vessel was weighed 5.52 g of Zn-powder (84.75 mmol=1.00eq), 7.86 g of triphenylphosphine (30.00 mmol=0.35 eq) and 0.84 g ofNiBr₂ (3.77 mmol=0.04 eq). After flushing the Schlenk vessel withnitrogen, 40 mL of dimethyl formamide was added and the suspension washeated for 30 min at 50° C. The mixture turned to reddish brown duringcomplex formation. To the mixture was added dropwise 15.00 g of4-bromo-2-methylthiophene (84.75 mmol=1.00 eq) and the mixture wasstirred overnight at 50° C. To the dark brown mixture was added 180 mLof cyclohexane. After 5 min stirring at 50° C., 100 mL of aqueous HCl(37%) was added slowly. The mixture was stirred for 30 min at 50° C. andthe acidic layer was removed. The cyclohexane layer was extracted againwith aqueous HCl (37%). The mixture was kept at 50° C. to preventprecipitation of bis-methylthiophene. The cyclohexane layer was washedtwice with water.

The organic layer was collected and the 2,2′-dimethyl-4,4′-dithienylcrystallised at cooling to room temperature. The crystals were collectedon a P4 glass filter. Small amounts (1-5%) of side products asphenylmethylthiophene, triphenylphosphine anddiphenyl(methylthiophenyl)phosphine were formed during synthesis.Yield=7.29 g. (37.6 mmol), (87.2%), 100% conversion

Step b) 2,5dimethyl-7H-thieno[3′,2′:3,4]cyclopenta[1,2-b]thiophen-7-one

To a solution of 40 g of tetrahydrofuran and 7.7 g (39.7 mmol) of2,2′-dimethyl-4,4′-dithienyl was added 32.3 mL of BuLi (80.8 mmol) at−20° C. keeping the temperature −6° C. After addition the temperaturewas kept at −10° C. for 1 h and then for 15 min at room temperature.Then the mixture was cooled to −20° C. and 4.3 g (39.7 mmol) of carbamylchloride was added keeping the temperature below −6° C. One h afteraddition the mixture was cooled to −75° C. and was stirred at thattemperature for 4 h. Then 5 mL of water was added at that temperatureand the cooling bath was removed. At room temperature 100 mL of waterwas added and the mixture was extracted twice with 50 mL of CH₂Cl₂. Theorganic layer was concentrated and the resulting solid was crystallizedfrom hexane/toluene 90/10 (v/v) yielding 5.7 g of the desired ketonewith a purity of ca 99%. Yield 84%

Step c) 2,5-dimethyl-7H-cyclopenta[1,2-b;3,4-b′]dithiophene

To a solution of 2.5 g (11.3 mmol) of ketone ex-step b1 in 25 mL ofdiethylene glycol at 120° C. was added 1.7 g (33.8 mmol) of hydrazinemonohydrate. This solution was stirred for 3 h and then 1.9 g (33.8mmol) of KOH in 6 g of water was added slowly (reflux condenser wasused) controlling the gas formation. After 2 h stirring the reaction wascomplete and workup was done by adding 200 mL of water and filtering offthe solid. The solids were washed 5 times with 10 mL of water. Afterdrying 2 g of a brown solid was isolated, being >99% pure2,5-dimethyl-7H-cyclopenta[1,2-b;3,4-b′]dithiophene (85% yield).

Example 6 Synthesis ofN-(tert-butyl)(dimethyl)(2-methyl-8H-indeno[2,1-b]thiophen-8-yl)silanamineZirconium dichloride

i) Synthesis ofchloro(dimethyl)(2-methyl-8H-indeno[2,1-b]thiophen-8-yl)silane

Suspension of 1.86 g (0.01 mol) 2-methyl-8H-indeno[2,1-b]thiophene in 25mL ether was treated dropwise with 6.25 mL (0.01 mol) of 1.6M BuLi inhexane at −40° C. under stirring. Then the mixture was stirred inadditional 3 h. The resulting mixture was treated with 1.20 mL (0.01mol) of dimethyldichlorosilane in 5 mL of ether at −70° C.; then it wasallowed to warm to r.t. and stirred overnight. The solution was isolatedand evaporated to give 2.47 g (89%) of the crude product that was usedwithout further purification.

¹H NMR (CD₆D₆, 30° C.) d: 7.57 (m, 2H), 7.33 (t, 1H), 7.18 (t, 1H), 6.85(m, 1H), 3.78 (s, 1H), 2.32 (s, 3H), 0.10 (s, 3H), 0.08 (s, 3H).

ii)N-(tert-butyl)(dimethyl)(2-methyl-8H-indeno[2,1-b]thiophen-8-yl)silanamine

A solution of 0.93 mL (0.0089 mol) of tert-butylamine in 30 mL of etherwas treated dropwise with 5.55 mL (0.0089 mol) of 1.6M BuLi in hexane at−30° C. The reaction mixture was stirred at r.t. for 3 h and theresulting suspension was treated with a solution of 2.47 g (0.0088 mol)of chloro(dimethyl)(2-methyl-8H-indeno[2,1-b]thiophen-8-yl)silane in 10mL of ether at −70° C. The resulting suspension was allowed to warm tor.t. and was stirred overnight. The solution was separated from LiCl andevaporated. The residue was treated with 60 mL hexane, the solution wasisolated and evaporated. Yield 1.98 g (71%) of crude product as red oil.

¹H NMR (C₆D₆, 30° C.) d: 7.67 (d, 1H), 7.62 (d, 1H), 7.39 (t, 1H), 7.27(t, 1H), 6.96 (m, 1H), 3.81 (s, 1H), 2.40 (s, 3H), 1.18 (s, 9H), 0.19(s, 3H),−0.14 (s,3H).

iii)N-(tert-butyl)(dimethyl)(2-methyl-8H-indeno[2,1-b]thiophen-8-yl)silanamineZirconium dichloride

To a solution of 1.98 g (0.0062 mol)N-(tert-butyl)(dimethyl)(2-methyl-8H-indeno[2,1-b]thiophen-8-yl)silanaminein 30 mL of ether 26 mL (0.0312 mol) of 1.2M MeLi in ether was added at−40° C. under stirring. Then the reaction mixture was stirred underreflux for 3 h. The resulting mixture was cooled to −60° C. and asolution of 0.68 mL (0.0062 mol) of TiCl₄ in 30 mL of hexane was added.The mixture was allowed to warm to r.t. and was stirred overnight. Theresulting mixture was evaporated, the residue was extracted with hexane(3 times with 50 mL).

The hexane solution was concentrated to a volume of 10 mL and kept 10hours at r.t. The crystalline product was separated from mothersolution, wished twice with cold pentane and dried. Yield 0.48 g (20%)of orange crystals.

¹H NMR (C₇D₈, 30° C.) d: 7.57 (d, 1H), 7.49 (d, 1H); 7.12 (dd, 1H); 6.92(dd,1H);6.71 (q, 1H); 2.24 (d, 3H); 1.43 (s, 9H); 0.63 (s, 3H); 0.61 (s,3H); 0.32 (s, 3H); −0.06 (s,3H) ¹³C NMR (C₇D₈, 30° C.) d: 146.8; 141.9;136.3; 135.9; 128.6; 126.6; 125.2; 125.0; 123.6; 79.5; 58.3; 57.5; 56.9;34.5; 16.4; 4.5; 4.2

1. A process for preparing a cyclopentadiene derivative having formula(I)

wherein T¹is selected from the group consisting of oxygen (O), sulphur(S) and NR, wherein R is selected from the group consisting of linear orbranched saturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl,C₆-C₂₀-aryl, C₇-C₂₀-atkylaryl, and C₇-C₂₀-arylalky radical, optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; R¹, R², equal to or different from each other arehydrogen or a linear or branched saturated or unsaturated C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkylradical, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; or they can form a C₄-C₇ ringoptionally containing O, S, N, P or Si atoms that can bear substituents;W is a moiety of formula (a) or (b)

wherein T², T³, T⁴, T⁵ equal to or different from each other areselected from the group consisting of nitrogen (N) and CR³ wherein R³ ishydrogen or a linear or branched saturated or unsaturated C₁-C₂₀-alkyl,C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-atkylaryl or C₇-C₂₀-arylalkylradical, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; or two adjacent R³ groups can form aC₄-C₇ ring optionally containing O, S, N, P or Si atoms, wherein saidring can bear substituents; T⁶ has the same meaning as T¹; T⁷ and T⁸equal to or different from each other are selected from N and CR³wherein R³ is hydrogen or a linear or branched saturated or unsaturatedC₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl orC₇-C₂₀-arylalkyl radical, optionally containing heteroatoms belonging togroups 13-17 of the Periodic Table of the Elements; optionally twoadjacent R³ groups can form a C₄-C₇ ring optionally containing O, S, N,P or Si atoms, said ring can bear substituents; with the proviso thatwhen T⁶ is different from NR, T⁷ and T⁸ are both CR^(3;) said processcomprising the following steps: a) reacting a compound of formula (II)

with a compound of formula (III)

in the presence of a coupling system, wherein X is selected from thegroup consisting of chlorine, iodine, and bromine; thereby forming acompound of formula (IV)

b) contacting the compound of formula (IV) with a carbonylating system;thereby forming a compound of formula (IVa)

and; c) treating the compound of formula (IVa) with a reducing agent. 2.The process according to claim 1 for preparing the cyclopentadienecompounds of formula (Ia)

comprising the following steps: a) reacting the compound of formula (II)

with a compound of formula (V)

in the presence of a coupling system, wherein X is selected from thegroup consisting of chlorine, iodine, and bromine; thereby forming acompound of formula (VI)

b) contacting the compound of formula (VI) with a carbonylating system;thereby forming a compound of formula (VIa)

and c) treating the compound of formula (VIa) with a reducing agent andrecovering the product.
 3. The process according to claim 1 wherein T¹is sulphur or oxygen; T² is NCH₃ or CH; T³, T⁴, T⁵ are CH; R¹ and R² areselected from the group consisting of hydrogen, methyl, ethyl, phenyl,and trimethylsilyl, or together form a benzene ring.
 4. The processaccording to claim 1 for preparing the cyclopentadiene compounds offormula (Ib)

comprising the following steps: a) reacting the compound of formula (II)

with a compound of formula (VII)

in the presence of a coupling system, wherein X is selected from thegroup consisting of chlorine, iodine, and bromine; thereby forming acompound of formula (VIII)

b) contacting the compound of formula (VIII) with a carbonylatingsystem; thereby forming a compound of formula (VIIIa)

c) treating the compound of formula (VIIIa) with a reducing agent andrecovering the product.
 5. The process according to claim 4 wherein T¹and T⁶ are the same and they are sulfur or oxygen; T⁷ and T⁸ equal to ordifferent from each other are CR^(3;) and R¹ and R² are hydrogen,methyl, ethyl, phenyl, trimethylsilyl group or together form a benzenering.
 6. The process according to claim 1 wherein step a) comprises thefollowing substeps: i) contacting the compound of formula (II) withmagnesium to form a corresponding Grignard reagent; and ii) contactingthe Grignard reagent formed in step i) with the compound of formula(III) in the presence of a compound selected from the group consistingof [1,3-bis(diphenylphosphino)propane]dichloronickel (dpppNiCl2),[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium (dppfPdCl2), andtetrakis(triphenylphosphino)palladium.
 7. The process according to claim1 wherein step a) comprises the following substeps: i) contacting thecompound of formula (III) with magnesium to form a correspondingGrignard reagent; and ii) contacting the Grignard reagent formed in stepi) with the compound of formula (II) in the presence of a compoundselected from the group consisting of[1,3-bis(diphenylphosphino)propane]dichloronickel (dpppNiCl2),[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium (dppfPdCl2), andtetrakis(triphenylphosphino)palladium.
 8. The process according to claim1 wherein step b) comprises the following substeps: i) contacting thecompound of formula (IV) with two equivalents of a base, thereby forminga dianionic compound; and ii) treating the dianionic compound with acompound of formula (IX)

wherein R⁴ and R⁵ equal to or different from each other are selectedfrom the group consisting of hydrogen, chlorine, bromine, iodine, OR andN(R)2.
 9. The process according to claim 8 wherein in the compound offormula (IX), R⁴ is chlorine, bromine, iodine, CF₃, Cl₃ or OR; and R⁵ isselected from the group consisting of CF₃, Cl₃, OR and N(R)2.
 10. Theprocess according to claim 1 wherein step b) comprises the followingsubsteps: i) contacting the compound of formula (IV) with two equivalentof a base and subsequently with one equivalent of a compound selectedfrom chlorine, bromine or iodine; thereby forming an anionicmonohalogenated derivative; and ii) treating the anionic monohalogenatedderivative obtained from step i) with a compound of formula (IXa)[M_(m)L_(j)(CO)_(n)]^(a)  (IXa) wherein M is a transition metal ofgroups 4-11 of the periodic table; L is a ligand that coordinates themetal M that can be neutral or with a positive or negative charge; aranges from −4 to +4 and represents the charge of the complex; whereinwhen a is 0 the complex is neutral; m ranges from 1 to 20; j ranges from0 to 30; and n ranges from 1 to
 50. 11. The process according to claim 1wherein step b) comprises the following substeps: i) contacting thecompound of formula (IV) with a halogenating compound and subsequentlywith one equivalent of a base; thereby forming an anionicmonohalogenated derivative; and ii) treating the anionic monohalogenatedderivative with a compound of formula (IXa)[M_(m)L_(j)(CO)_(n)]^(a)  (IXa) wherein M is a transition metal ofgroups 4-11 of the periodic table; L is a ligand that coordinates themetal M that can be neutral or with a positive or negative charge; aranges from −4 to +4 and represents the charge of the complex; whereinwhen a is 0 the complex is neutral; m ranges from 1 to 20; j ranges from0 to 30; and n ranges from 1 to
 50. 12. The process according to claim 4wherein the compounds of formula (II) and (VII) are the same and thecoupling system comprises: i) an alkali or alkaline earth-metal; ii) acompound of formula Q(G)₃ or a compound of formula (G)₂Q-A-Q(G)₂ whereinQ is a phosphorus or nitrogen atom, G equal to or different from eachother are selected from the group consisting of linear or branchedsaturated or unsaturated C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl, C₆-C₂₀-aryl,C₇-C₂₀-alkylaryl, and C₇-C₂₀-arylalkyl radical, optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements and A is a group linking the two Q atoms chosen from a divalentorganic radical selected from the group consisting of C₁-C₂₀-alkylene,C₃-C₂₀-cycloalkylene, C₂-C₂₀-alkenylene, C₆-C₂₀-aryleneC₇-C₂₀-alkylarylene, and C₇-C₂₀-arylalkylene divalent radical,optionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements, or a complex that has the two radicalsQ(G)2 as substituents; and iii) a transition metal halogenide of formulaJZ_(e) wherein J is a transition metal; Z is chlorine, bromine, oriodine; and e is equal to the oxidation state of the metal J.
 13. Theprocess according to claim 12 wherein the coupling system comprises: i)Zinc powder or granules; ii) triphenylphosphine; and iii) NiBr₂.
 14. Theprocess according to claim 11 wherein the base used in step b) isselected from hydroxides and hydrides of alkali- and alkaline-earthmetals, metallic sodium and potassium and organometallic lithiumcompounds.
 15. The process according to claim 1 wherein the reductionstep c) comprises the following substeps: i) contacting the compound offormula (IV) with N₂H₄; ii) adding a solution of KOH in water; and iii)filtering the solid and recovering the product.
 16. The processaccording to claim 1, wherein X is bromine.
 17. The process according toclaim 2, wherein X is bromine.
 18. The process according to claim 12,wherein J is a transition metal of groups of the Periodic Table.